Device-To-Device Communication

ABSTRACT

There is provided a solution for improving the quality of service of end-to-end communication between at least two user terminals. The solution comprises applying uplink signaling in which information related to the traffic status of a direct device-to-device communication link is transmitted.

FIELD

The invention relates generally to mobile communication networks. Moreparticularly, the invention relates to device-to-device communication ina communication network.

BACKGROUND

Generally, in a mobile communication network, such as the Long TermEvolution (LTE) or the LTE-Advanced (LTE-A) of the 3^(rd) GenerationPartnership Project (3GPP), two user terminals communicate with eachother via a base station (evolved Node B (eNB) in the LTE). However, therequirements for efficient use of network resources and the needs fornew services or service models may lead to applying directdevice-to-device (D2D) communication. The D2D communication, ormobile-to-mobile, terminal-to-terminal, or peer-to-peer communicationmay be employed within the mobile communication network.

The direct D2D communication comprises at least two relatively closelylocated devices communicating with each other directly instead of aconventional communication link for end-to-end (E2E) communication, inwhich the source device transmits data to the destination device via theeNB. The two devices in the D2D communication may apply radio resourcesof the mobile communication network, thus sharing the resources withdevices that are communicating with the eNB in the conventional link.This may lead to challenges in the radio resource allocation performedby the eNB. Further, the quality of service (QoS) of the E2Ecommunication may suffer from the decisions related the radio resourceallocation, a data transport method (the D2D communication link versusthe conventional link), and the like, governed by the eNB.

Consequently, for the sake of performing reliable D2D communication,reducing transmitter power, increasing the capacity and coverage of thenetwork, and creating and supporting services for the users, it isimportant to provide a solution for more efficient use of the D2Dcommunication in a mobile communication network.

BRIEF DESCRIPTION OF THE INVENTION

An object of the invention is to provide a solution for more efficientuse of direct device-to-device communication.

According to an aspect of the invention, there is provided a method asspecified in claim 1.

According to an aspect of the invention, there are provided apparatusesas specified in claims 15 and 29.

According to an aspect of the invention, there is provided a computerprogram product as specified in claim 30.

Embodiments of the invention are defined in the dependent claims.

LIST OF DRAWINGS

In the following, the invention will be described in greater detail withreference to the embodiments and the accompanying drawings, in which

FIG. 1 presents a communication network according to an embodiment;

FIG. 2 presents a communication network employing a direct communicationlink according to an embodiment;

FIG. 3 shows a communication network employing a direct communicationlink according to an embodiment;

FIG. 4 illustrates a communication network employing a directcommunication link according to an embodiment;

FIG. 5 illustrates use of sequence numbers according to an embodiment;

FIG. 6 shows a block diagram of an apparatus according to an embodiment;

FIG. 7 illustrates a method for applying uplink signaling according toan embodiment;

FIG. 8 presents a method for controlling the quality of service of thecommunication, according to an embodiment; and

FIG. 9 presents a method for transmitting the uplink signaling accordingto an embodiment.

DESCRIPTION OF EMBODIMENTS

The following embodiments are exemplary. Although the specification mayrefer to “an”, “one”, or “some” embodiment(s) in several locations ofthe text, this does not necessarily mean that each reference is made tothe same embodiment(s), or that a particular feature only applies to asingle embodiment. Single features of different embodiments may also becombined to provide other embodiments. Although this invention isdescribed using LTE (or Evolved universal mobile telecommunicationssystem (UMTS) terrestrial radio access network (UTRAN) as a basis, itcould be applicable to any other wireless mobile communication systemsas well. For example, the embodiments may be applied under the UMTS orthe Global system for mobile communications (GSM), etc. Thetelecommunication system may have a fixed infrastructure providingwireless services to subscriber terminals:

FIG. 1 illustrates possible methods for communication in a mobilecommunication network. The communication network may comprise a basestation 100. The base station 100 may provide radio coverage to a cell102, control radio resource allocation within the cell 102, perform dataand control signaling, etc. The cell 102 may be a macro cell, a microcell, or any other type of cell where radio coverage is present.Further, the cell 102 may be of any size or form depending on theantenna aperture. That is, it may not be of oval or circular form, butany other form is applicable to embodiments. The cell 102 controlled bythe base station 100 may be divided into sectors, but such a scenario isnot illustrated in greater detail in order to keep the focus on theinvention.

The base station 100 may be used by multiple network operators in orderto provide radio coverage from multiple operators to the cell 100. Thebase station 100 may be a node B, an evolved node B (eNB) as in LTE-A, aradio network controller (RNC), or any other apparatus capable ofcontrolling radio communication within the cell 102. In the case ofmultiple base stations in the communication network, the base stationsmay be connected to each other with an X2 interface and via S1 interfaceto an evolved packet core (EPC), more specifically to a mobilitymanagement entity (MME) and to a serving gateway (S-GW). The MMEcontrols the functions of non-access stratum signaling, roaming,authentication, tracking area list management, etc., whereas the S-GWhandles functions including packet routing and forwarding, E-UTRAN idlemode packet buffering, etc.

Referring to FIG. 1, the cell 102 is associated with the base station100 controlling communications within the cell 102. The base station 100may control a cellular radio communication link established between thebase station 100 and terminal devices 110 to 112 located within the cell102. As explained in the background section, a conventionalcommunication link for end-to-end communication is such where the sourcedevice transmits data to the destination device via the base station100. That is, radio communication links 114 and 116 are establishedbetween the terminal device 110 and the base station 100, and betweenthe terminal device 112 and the base station 100, respectively.Therefore, the user terminals 110, 112 may communicate with each othervia the base station 100.

According to an embodiment, direct device-to-device (D2D) connectionsmay be established among terminal devices. Direct communication linksbetween two devices are established, e.g., between terminal devices 120and 122 in FIG. 1. A direct communication link 124 may be based on anyradio technology such that the terminal devices 120 and 122 involved inthe direct communication may apply communication according to any of aplurality of radio access technologies.

According to an embodiment, the base station 100 may be responsible forcontrolling the direct communication link 124, as shown with dashed,bi-directional lines in FIG. 1. The radio access technology of thedirect communication link 124 may operate on the same frequency band asthe conventional communication link and/or outside those frequency bandsto provide the arrangement with flexibility. Thus, the base station 100may be responsible for allocating radio resources to the directcommunication link 124 as-well as for the conventional communicationlinks 114 and 116. For example, the cellular network may operate in FDDduplex mode and the direct communication link 124 may apply TDD duplexmode utilizing uplink, downlink or uplink and downlink radio resourcesof the cellular network under the control of the base station 124.

FIG. 2 shows a mobile communication network according to an embodiment.The network comprises a base station 200 and two user terminals 220 and222. The user terminal 220, 222 may be a palm computer, user equipmentor any other apparatus capable of operating in a mobile communicationnetwork. Even though the user terminals 220, 222 could applyconventional communication via the base station 200, they cancommunicate directly with each other via a D2D direct communication link224. According to an embodiment, the two user terminals 220, 222 are theterminating points of the communication. The direct communication linkmay be utilized during a service or a call, for example.

The direct communication link 224 may be established by the base station200 that provides radio coverage to the cell in which the user terminals220, 222 are located. That is, the base station 200 may establish theconnection 224 by controlling the operations of the user terminals 220,222 via bi-directional control channels 204 and 206, as shown in FIG. 2.Further, the base station may be responsible for radio bearer control ofthe cellular network. The radio bearer is used to carry data with acertain QoS requirements, for example for a certain application. Theuser terminals 220, 222 may be in RRC connected state and, therefore,connected to the base station at least for control purposes via thecontrol links 204, 206.

In order to facilitate efficient resource allocation and to provideadequate E2E QoS to the UEs utilizing possible direct D2D communicationsduring the service or call, there is a need for the base station to knowabout the traffic demand, status and performance of the direct D2Dcommunication link. In addition, sufficient monitoring of the D2Dconnection is desirable for fair charging and possible legal issues inpublic networks which require having a mechanism in place to monitoractive users. Because the direct communication mode considered herein ismeant for E2E communications where the two user terminals are theterminating points of the data communication, the base station may notbe able to monitor the actual status and traffic performance over theD2D connection directly but rely on reporting from the involved UEs.Thus, according to an embodiment, the base station relies on reportsobtained from the at least one user terminal in order to monitor the D2Dcommunication link.

According to an embodiment, at least one user terminal 220, 222 and thebase station 200 apply uplink signaling 208 in the mobile communication,wherein the signaling comprises information related to the trafficstatus of the direct communication link 224 between two user terminals220, 222. That is, the information may be related to how actively andhow well the communication link 224 is applied in communication of datapackets between the user terminals 220, 222.

In addition, the information may be further related to functionalitiesof the radio-interface data link layer (layer 2) or above of at leastone user terminal 220, 222 involved in the direct communication link224. That is, at least one of the user terminals 220, 222 informs thebase station via the uplink 208 about the status of the layer 2 orabove. The layer 2, in the radio interface of a radio access network,such as UTRAN or E-UTRAN, often consists of a medium access control(MAC) sub-layer and a radio link control (RLC) sub-layer on top of MAC.In addition, a packet data convergence protocol (PDCP) on top of RLC maybe considered as a sub-layer of the layer 2 as well. The layer 2 isresponsible for in-order, reliable and secured data-packet transferbetween peer-to-peer network entities. The layer 2 may adoptretransmission mechanisms, such as automatic repeat request (ARQ) and/orhybrid automatic repeat request (HARQ) protocols for detecting andcorrecting or recovering residual packet errors that may occur in thephysical layer or that may be left by the physical layer. Theinformation related to the layer 2 may thus comprise knowledge regardingthe successfulness of the data transfer as well as the status of thetransmitter/receiver data buffers on the radio bearer basis. In otherwords, the information transmitted in the uplink 208 may, according toan embodiment, comprise information to be monitored on the layer 2 ofthe connection between the two user terminals 220 and 222.

The information may comprise at least one of the following: transmitterbuffer status, sequence number of the last arrived data packet, sequencenumber of the last transmitted data packet, sequence number of the lastin-sequence received data packet, sequence numbers of at least oneout-of-sequence received data packet and sequence numbers of at leastone missing data packet, on the radio bearer basis of the userterminals. The data packet may correspond to a packet data convergenceprotocol (PDCP) packet. According to an embodiment, these items may becomprised in the transmitted information in any possible combination.That is, the information may comprise, for example, one, three or all ofthese items.

The transmitter buffer status may denote the status of the buffer ofeither the user terminal 220 or the user terminal 222, or the buffers ofboth of the user terminals 220 and 222. For example, the total amount ofdata found in the buffer may be reported to the base station 200. Thebuffer may be used to store data packets to be transmitted via thedirect communication link 224 on the radio bearer basis.

FIG. 5 illustrates exemplary use of sequence numbers. The data packetsthat are transmitted to the other end of the direct communication linkmay be identified with the sequence numbers 500 to 514 at thetransmitter. Then, the receiver of the data packet may extract thesequence number 500 to 514 from the received data packet. Further, thetransmitter may inform the receiver about the total number of datapackets that are to be transmitted (instead of the total amount of datavolume as for the buffer status in case data packets have preconfiguredequal sizes). The sequence numbers 500 to 514 may thus be used indetermining if all of the data packets have been received. Further, thesequence numbers 500 to 514 may be applied in determining the lastin-sequence received data packet. In-sequence denotes that the sequencenumber of the received data packet follows the pattern of the previouslyreceived data packets. For example, in the case when the receivedsequence numbers are 1, 2, 3, 8 and 4, the last in-sequence receiveddata packet is the data packet identified with the sequence number 4(the received data packets are re-ordered in the receiver). Further, thesequence numbers of the at least one out-of-sequence received datapacket are, in this case, the sequence number 8. The at least onemissing data packet is, in this case, the data packets identified withsequence numbers 5, 6 and 7.

Let us take another look at FIG. 2. According to an embodiment, a userterminal 222 determines the information and transmits the information inthe uplink 208. That is, the user terminal 222 transmits the informationrelated to the traffic status of the direct communication link 224concerning both the user terminals 220 and 222 on the radio bearer basisvia the uplink 208. The user terminal 222 may transmit the informationin the uplink on the MAC layer or above, including the option of usingradio resource control (RRC) signaling.

According to an embodiment, the user terminal 222 may be configured totransmit the information in uplink periodically. That is, after apredetermined time the user terminal 222 transmits the information tothe base station. Further, the transmission of information may occurafter a predefined event, as the user terminal is configured orrequested. For example, if the transmitter buffer reaches apredetermined level, the user terminal 222 may be triggered to transmitthe information to the base station 200 via 208. The user terminal mayalso gather the information and transmit it to the base station uponreceiving a request from the base station. In addition, the transmissionof information may occur periodically after some predefined or specifiedevent has occurred. The period for transmission may be adaptively variedduring the communication.

According to an embodiment, the user terminal 222 may collect theinformation from the other user terminal 220 involved in the directcommunication link. The user terminal 222 may request the user terminal220 to transmit the information to the user terminal 222 via a link 226.Alternatively, the information may be transmitted from the user terminal220 to the user terminal 222 via the direct communication link 224already established.

Further, the user terminal 222 may then transmit the collectedinformation in the uplink. The user terminal 222 may then transmit thecollected information together with the information gathered by itself,that is from its own layer 2, from its own sequence number information,from its own transmitter buffer, and the like.

That is, both of the user terminals 220, 222 of the direct communicationlink 224 may determine the information. However, the information may betransmitted in the uplink to the base station by only one of the userterminals 220, 222 of the direct communication link 224.

However, as shown in FIG. 3, according to another embodiment, both ofthe user terminals 320 and 322 involved in the direct communication link324 may transmit the information to the base station 300 in the uplinkvia uplink channels 304 and 306, respectively. That is, the transfer ofthe information between the user terminals 320, 322 may not take place,because both user terminals 320, 322 transmit the information directlyto the base station.

According to an embodiment, the transmission of the information frommore than one user terminal involved in the direct communication maytake place simultaneously in a synchronized manner, as configured andcontrolled. According to another embodiment, the transmission of theinformation from one user terminal may take place at a predefined timeoffset compared to another user terminal. For example, the user terminal320 may transmit the information with a predetermined time offsetcompared to the user terminal 322.

By transmitting the information related to the traffic status of thedirect communication link on the radio bearer basis in the uplink, thereceiving base station may obtain knowledge it can apply in controllingthe resource allocation and quality of service of end-to-endcommunication between the two user terminals. This controlling alsoincludes possible switching back and forth between the supportedradio-connectivity-and-operation modes of using a conventional cellularlink via the base station or using direct D2D communication link, orusing both. The end-to-end communication denotes the communicationbetween two user terminals on a certain application level, eitherdirectly between the two user terminals or via the base station in theconventional communication method.

By transmitting the information related to the traffic status of thedirect communication link on the radio bearer basis in the uplink, thereceiving base station may obtain knowledge on the data volume ofongoing device-to-device communication and report the data volume tocore network for e.g. charging purpose.

Looking back to FIG. 2, according to an embodiment, the base station 200receives the information on the MAC layer or above including the optionof using radio resource control (RRC) signaling. The information may berelated to the traffic status of the direct communication link 224between the two user terminals 220, 222, and further related to thefunctionalities of the layer 2 of at least one of the two user terminals220, 222 involved in the direct communication link 224.

According to an embodiment, the base station configures and controls theuser terminal monitoring and uplink signaling reports from the at leastone user terminal 220, 222. Consequently, the base station 200 receivesthe uplink signaling from the at least one UE. The base station 200 mayreceive information periodically or in an event-triggered fashion. Theevent that triggers the transmission of information can be determinedbeforehand in the configuration of the mobile communication network. Anexemplary event could be a fulfillment of the transmitter buffer up to acertain threshold. Further, the base station 200 may request either ofthe user terminals 220, 222 to transmit the information at any point ofthe communication.

Further, the base station 200 controls the user terminal reporting suchthat it receives the information from one user terminal only, or frommore than one user terminal 220, 222. In a case the base station 200receives the information from both of the user terminals 220, 222, thebase station 200 may control the reporting such that the base station200 receives the information simultaneously from both user terminals220, 222, or first from one user terminal and, after a time offsetdelay, from the other user terminal. According to the embodiment, thebase station 200 obtains knowledge of the traffic status on the ongoingdirect communication link 224 between the two user terminals 220, 222,on the basis of the received information in the uplink channel 208.Further, the base station 200 may determine the D2D communication linkperformance including the progress of the corresponding radio bearers:their current data buffer status, up-to-date packet losses, and soforth.

The base station 200 may then be able to control the quality of service(QoS) of the end-to-end communication between the two user terminals220, 222 on the basis of the received information. In other words, thebase station 200 may, during a service or a call, control switching backand forth between the two modes: either using conventional links 210 forcommunication via the base station, using D2D communication links 224without routing data through the base station 200, or using both ofthese modes simultaneously. This can be considered as a part of userterminal connection management and QoS control. Further, the basestation is responsible for setting up, configuring and reconfiguringcorresponding radio bearer(s) for each mode. The base station may alsobe responsible for controlling and scheduling data transmissions of eachradio bearer to provide required QoS. Namely, the end-to-endcommunication does not denote simply the direct communication link 224,but also the conventional communication link 210 via the base station200. The QoS denotes that the user terminals involved in thecommunication can employ sufficient resources in order to keep thecommunication reliable and free of unnecessary delays. Further, itdenotes the ability to provide different priorities to different dataflows, and to guarantee a certain level of performance to any data flow.For example, a required bit rate and packet dropping probability and/orbit error rate may be kept within certain predetermined limits.

According to an embodiment, the base station 200 may redistribute radioresources of the mobile communication on the basis of the receivedinformation. For example, the base station 200 may temporarily allocatemore resources to the direct communication link 24 if the informationreceived implies that the level of the traffic is high in the directcommunication link 224 or there are more than a certain threshold numberof missing packets in the communication between the two user terminals220, 222.

It can be understood that at the establishment of the directcommunication link 224, the base station has allocated a certain numberof radio resources to the link 224, that is a certain number of radioresources that the user terminals 220, 222 involved in the directcommunication link may use. The radio resources may be allocated in afrequency, time, spatial and/or code domain. That is, the communicationlink 224 may apply a certain frequency range, a certain time frame, acertain spatial orientation, or a certain code to distinguish the directcommunication link 224 from other communications taking place in thevicinity of the direct communication link 224. Thus, after receiving areport of information in the uplink 208, the base station 200 mayreallocate the radio resources such that sufficient quality of serviceis ensured for the direct communication link 224. For example, the basestation 200 may allocate more resources to the direct communication link224 if the traffic situation on the link requires more resources. If thetraffic situation in the link 224 is lower than current radio resourceswould allow, the base station 200 may release some of the resourcesallocated to the link 224 such that they can be allocated to differentcommunication links within the cell in which the base station 200provides radio coverage. Alternatively, the base station 200 may decidethat no redistribution of radio resources is needed at this point if thetraffic situation and quality of the direct communication link is suchthat the number of radio resources allocated to the link 224 is ofappropriate amount.

According to an embodiment, the base station 200 may decide whether toapply the conventional radio communication link 210 via the base station200 or the direct communication link 224 between the two user terminals220, 224 or not, on the basis of the received information. That is, thebase station 200 may make the decision on the basis of the receivedtraffic status and layer 2 information. For example, if the informationimplies that the traffic between the user terminals 220, 222 is suchthat the packet error rate or the like is above a predefined threshold,the direct communication link 224 may be stopped and the communicationconnection is switched to use the conventional communication link 210via the base station 200, on the radio bearer basis. This is alsoreferred to as mode switching or mode reselection between the directmode and the conventional mode.

The base station 200 may further apply information related to thecondition of the link 224 in making the decision whether to apply theconventional radio communication via the base station 200 or the directcommunication between the two user terminals 220, 224 or not, or whetherto redistribute the radio resources. That is, the invention does notexclude the use of information related to link 224 quality metrics, suchas time/frequency variance, a signal-to-noise ratio (SNR), etc, inaddition to the information related to at least one of the following:the traffic status, the data flow and the layer 2.

In an embodiment, as shown in FIG. 4, one 420 of the two user terminals420, 422 is located in a radio coverage area 402 of a base station 400and the other 422 of the two user terminals 420, 422 is located in aradio coverage area 412 of a different base station 410. Regardless ofthis, the user terminals 420, 422 may apply a direct communication link424. However, in this case the quality of service of the communicationbetween the two user terminals 420, 422 may be controlled by more thanone base station. For example, the link 424 may be controlled by twobase stations 400, 410, as shown with dotted lines 404 and 414,respectively.

In order to coordinate the control performed by the base stations 400,410, the base stations 400, 410 may communicate with each other. Thatis, according to an embodiment, a base station 400 communicates with atleast one other base station 410 in order to coordinate the quality ofservice of the end-to-end communication between the at least twoterminals 420, 422. The base station 400 may communicate with basestation 410 via, for example, the X2 interface 440 of the LTE. The basestations 400, 410 may keep each other updated of the layer 2 statusinformation of the direct communication link 424, such as the packetdata convergence protocol (PDCP) level report on the radio bearer basisreceived from at least one user terminal 420, 422. Here the basestations 400, 410 may control the QoS of the communication between theuser terminals 420 and 422 by redistributing radio resources within thetwo cells 402 and 412, or by performing mode switching from the directmode to the conventional mode.

According to an embodiment, the controlling base station may be involvedin performing conventional handover for a user terminal involved in thedirect communication link from one cell to another cell, in addition tocontrolling the QoS of the communication between the at least twoterminals.

According to an embodiment, FIG. 5 can be seen to comprise data packetsin one radio bearer. That is, the radio bearer shown in FIG. 5 maycomprise data packets identified with sequence numbers 500 to 514. Adifferent number of sequence numbers may be applied by another radiobearer. The radio bearer is used to carry certain type of data from atransmitter to a receiver. A certain radio bearer may require certainquality of service. The at least one user terminal may communicate theinformation related to the traffic status of the direct communicationlink between at least two terminals on the radio bearer basis. That is,the user terminal transmitting the information in the uplink maytransmit the information for each radio bearer. For example, the userterminal may transmit the sequence number of the last in-sequencereceived data packet in a radio bearer. Then the receiving base stationmay control the QoS of the end-to-end communication in a radio bearerspecific manner.

A very general architecture of an apparatus according to an embodimentof the invention is shown in FIG. 6. FIG. 6 shows only the elements andfunctional entities required for understanding the apparatus accordingto an embodiment of the invention. Other components have been omittedfor reasons of simplicity. The implementation of the elements andfunctional entities may vary from those shown in FIG. 6. The connectionsshown in FIG. 6 are logical connections, and the actual physicalconnections may be different. It is apparent to a person skilled in theart that the apparatus for applying the uplink signaling may alsocomprise other functions and structures.

According to an embodiment, the apparatus 600 is comprised in a userterminal of a mobile communication network. According to anotherembodiment, the apparatus 600 is comprised in a base station of a mobilecommunication network.

The apparatus 600 for applying the uplink signaling may comprise aprocessor 602. The processor 602 may be implemented with a separatedigital signal processor provided with suitable software embedded on acomputer readable medium, or with a separate logic circuit, such as anapplication specific integrated circuit (ASIC). The processor 602 maycomprise an interface, such as computer port, for providingcommunication capabilities.

The processor 602 may be configured to apply uplink signaling to mobilecommunication, wherein the signaling comprises information related tothe traffic status of a direct communication link between at least twoterminals. Further the signaling may be related to functionalities ofthe layer 2 of at least one user terminal involved in the directcommunication link.

Further, according to an embodiment, the processor 602 is applicable toa user terminal involved in a direct communication link between at leasttwo terminals. Then, the processor 602 may determine the informationrelated to the traffic situation and layer 2, and transmit theinformation in the uplink.

The apparatus 602, applicable to a user terminal, may be configured tomanage a cache buffer beside the conventional layer 2transmission-and-reception buffers in order to re-transmit at least onedata packet already transmitted, as configured or if requested. Thecache buffer is designed for monitoring the contents of direct in-bandD2D communication, if desired. The buffer may be stored in a memory 604.The memory 604 may be connected to the processor 602. However, memorymay also be integrated to the processor 602 and, thus, the memory 604may not be required. The buffer may comprise one or more data packetstransmitted previously via the direct communication link, and theapparatus 602 may be requested to re-transmit one or more data packetsto the base station or to the other user terminal involved in the directcommunication link. The data packets requested to be re-transmitted maybe, for example, missing data packets.

Further, according to an embodiment, the processor 602 is applicable toa base station. Then, the processor 602 may control the quality ofservice of end-to-end communication between the at least two terminalson the basis of the received information. Further, the apparatus 602 maymanage a virtual radio bearer database corresponding to the actual radiobearers applied to the direct communication between the at least twoterminals. In addition, the apparatus may update the virtual radiobearer database on the basis of the received information related to thetraffic status and the MAC layer. The virtual radio bearer database maybe used when the mode switching from the direct communication mode tothe conventional communication mode takes place. The apparatus 600 maystore the virtual database in the memory 604, or store it directly inthe processor 602.

Further, when the processor 602 is applicable to a base station, theprocessor 602 may be in control of the cache buffer that is present inthe user terminal beside the conventional layer 2transmission-and-reception buffers in order to re-transmit at least onedata packet already transmitted, as configured or if requested. Theprocessor 602 may control for example the configuration and operation ofthe buffer. The processor 602 may, for example, configure the size ofthe buffer, different window sizes and/or timers to manage the buffer(e.g. to empty the buffer).

Further the processor 602 may give commands to the user terminal storingthe buffer to send any packets in the buffer to the apparatus 600 inorder to perform monitoring of the data traffic or re-transmissions viathe conventional communication method. According to an embodiment, theapparatus 600 controls re-transmissions of the direct communication linkbetween the two user terminals such that the re-transmissions areperformed through the conventional radio communication via the apparatus600. According to another embodiment, the apparatus controls there-transmission in the direct communication link if suchre-transmissions directly between the two user terminals are needed.According to another embodiment, the apparatus 600 controls, RLC (RadioLayer Control) layer re-transmissions of the direct communication linkbetween the two user terminals such that the RLC (Radio Layer Control)layer re-transmissions are performed through the conventional radiocommunication via the apparatus 600.

The apparatus 600 may further comprise a transceiver (TRX) 606. The TRX606 may further be connected to an antenna 608 enabling connection toand from an air interface. Alternatively, the antenna 608 may beconnetted to a wired interface. The TRX 606 may enable transmissionand/or reception of information.

FIG. 7 shows a method for applying the uplink signaling. The methodbegins in step 700. In step 702 the method comprises applying the uplinksignaling, in which information related to the traffic status of thedirect communication link between at least two terminals is transmittedfrom a user terminal involved in the direct communication link to thebase station. The method ends in step 704.

FIG. 8 illustrates a method for controlling the quality of service ofthe end-to-end communication between the at least two terminals at thebase station. The method begins in step 800. In step 802, the basestation receives the uplink signaling information related to the trafficstatus of the direct communication link. In step 803, the base stationmonitors data volume of ongoing end-to-end communication between atleast two user terminals on the basis of the received information. Thenthe base station determines the best course of action. In step 804A thebase station determines that the direct communication is not providingsufficient quality, and thus, the base station decides to switch to theconventional communication mode, in which communication between two userterminals is performed via the base station. Alternatively, in step804B, the base station decides to reallocate/redistribute the radioresources of the mobile communication network such that more or fewerradio resources are allocated to the direct communication link. Themethod ends in step 806.

FIG. 9 shows a method for applying the uplink signaling at the userterminal. The method begins in step 900. In step 902, the methodcomprises determining the information related to the traffic statusand/or to the layer 2 at the user terminal. Further, in case one userterminal applies the uplink signaling, step 904 takes place, in whichthe user terminal collects the information from the other userterminal(s) involved in the direct communication link. However, step 904may not be required in the case when each user terminal involved in thedirect communication transmits the uplink signaling. Then, the methodcomprises transmitting the information in the uplink in step 906. Themethod ends in 908.

Even though the description is given in most parts for two userterminals involved in the direct communication link, it isstraightforward to generalize the invention for a case where directcommunication is established between a plurality of user terminals.

The invention offers several advantages. For example, it allowsseparating the link and signal quality based uplink reporting from thedataflow related QoS management as described. The link and signalquality based management of radio resources requires a lot of signalingdue to the fact that channel quality information needs to be transmittedto the base station in order for the base station to make an informeddecision related to the quality of the communication, whereas thelatter, as described, needs only moderate signaling. Further, the linkand signal quality based management of radio resources is generallyperformed initially in the establishment of the link and quite seldomafterwards. The data traffic and layer 2 related QoS management asdescribed herein can be performed during on-going direct communicationbetween at least two terminals. According to an embodiment, most of theautomatic repeat request (ARQ) complexity can be performed in theconventional communication link instead of the direct communicationlink.

The techniques and methods described herein may be implemented byvarious means. For example, these techniques may be implemented inhardware (one or more devices), firmware (one or more devices), software(one or more modules), or combinations thereof. For a hardwareimplementation, the apparatus of FIG. 6 may be implemented within one ormore application-specific integrated circuits (ASICs), digital signalprocessors (DSPs), digital signal processing devices (DSPDs),programmable logic devices (PLDs), field programmable gate arrays(FPGAs), processors, controllers, micro-controllers, microprocessors,other electronic units designed to perform the functions describedherein, or a combination thereof. For firmware or software, theimplementation can be carried out through modules of at least one chipset (e.g. procedures, functions) that perform the functions describedherein. The software codes may be stored in a memory unit and executedby processors. The memory unit may be implemented within the processoror externally to the processor. In the latter case it can becommunicatively coupled to the processor via various means, as is knownin the art. Additionally, the components of the systems described hereinmay be rearranged and/or complimented by additional components in orderto facilitate the achieving of the various aspects, etc., described withregard thereto, and they are not limited to the precise configurationsset forth in the given figures, as will be appreciated by one skilled inthe art.

Thus, according to an embodiment, the apparatus for performing the tasksof FIGS. 2 to 4 and 7 to 9 comprises processing means for applying theuplink signaling, in which information related to the traffic status ofthe direct communication link between at least two terminals istransmitted from a user terminal involved in the direct communicationlink to the base station.

Embodiments of the invention may be implemented as computer programs inthe apparatus of FIG. 6 according to the embodiments of the invention.The computer programs comprise instructions for executing a computerprocess for improving the quality of service of the end-to-endcommunication between the at least two terminals. The computer programimplemented in the apparatus may carry out, but is not limited to, thetasks related to FIGS. 2 to 4 and 7 to 9.

The computer program may be stored on a computer program distributionmedium readable by a computer or a processor. The computer programmedium may be, for example but not limited to, an electric, magnetic,optical, infrared or semiconductor system, device or transmissionmedium. The computer program medium may include at least one of thefollowing media: a computer readable medium, a program storage medium, arecord medium, a computer readable memory, a random access memory, anerasable programmable read-only memory, a computer readable softwaredistribution package, a computer readable signal, a computer readabletelecommunications signal, computer readable printed matter, and acomputer readable compressed software package.

Even though the invention has been described above with reference to anexample according to the accompanying drawings, it is clear that theinvention is not restricted thereto but can be modified in several wayswithin the scope of the appended claims. Further, it is clear to aperson skilled in the art that the described embodiments may, but arenot required to, be combined with other embodiments in various ways.

1. A method, comprising: applying, by a mobile communication device,uplink signaling in mobile communication, wherein the signalingcomprises information determined by the device as related to a trafficstatus of a direct communication link between at least two userterminals being the terminating points of the communication; andtransmitting the information in the uplink to a base station from atleast one user terminal involved in the direct communication linkthereby enabling the base station to control the quality of service ofan end-to-end communication between the at least two user terminalsbased on the received information.
 2. The method of claim 1, wherein theinformation is related to a packet data convergence protocol.
 3. Themethod of claim 1, wherein the uplink signaling is applied on a mediumaccess control layer or on a radio resource control layer.
 4. The methodof claim 1, wherein the transmitting is performed periodically, after apredetermined event, or on request.
 5. (canceled)
 6. (canceled)
 7. Themethod of claim 1, further comprising: transmitting the informationsimultaneously in a synchronized manner, or at a predefined time offsetcompared to another user terminal when more than one user terminaltransmits the information.
 8. (canceled)
 9. The method of claim 1,further comprising: receiving the information at a base station;monitoring data volume of ongoing end-to-end communication between atleast two user terminals on the basis of the received information; andcontrolling the quality of service of end-to-end communication betweenthe at least two user terminals on the basis of the receivedinformation.
 10. The method of claim 9, further comprising:redistributing radio resources of the mobile communication on the basisof the received information.
 11. The method of claim 9, furthercomprising: deciding on the basis of the received information whether toapply conventional radio communication via the base station, the directcommunication between the at least two terminals, or both.
 12. Themethod of claim 9, further comprising: controlling the quality ofservice of the end-to-end communication between the at least two userterminals by more than one base station; and communicating with at leastone other base station in order to coordinate the quality of service ofthe end-to-end communication between the at least two terminals.
 13. Themethod of claim 9, further comprising: managing a virtual radio bearerdatabase corresponding to the radio bearers applied in the directcommunication between the at least two user terminals; and updating thevirtual radio bearer database on the basis of the received information.14. The method of claim 9, further comprising: controllingre-transmissions of the direct communication link between the at leasttwo user terminals such that the re-transmissions are performed throughthe conventional radio communication link via the base station.
 15. Anapparatus, comprising a processor configured to: apply uplink signalingin mobile communication, wherein the signaling comprises informationdetermined by the apparatus as related to the traffic status of a directcommunication link between at least two user terminals being theterminating points of the communication; and transmit the information inthe uplink to a base station from at least one user terminal involved inthe direct communication link thereby enabling the base station tocontrol the quality of service of an end-to-end communication betweenthe at least two user terminals based on the received information. 16.The apparatus of claim 15, wherein the information is related to apacket data convergence protocol.
 17. The apparatus of claim 15, whereinthe uplink signaling is applied on a medium access control layer or on aradio resource control layer.
 18. The apparatus of claim 15, wherein thethe transmitting is performed periodically, after a predetermined event,or on request.
 19. (canceled)
 20. (canceled)
 21. The apparatus of claim15, wherein the interface is further configured to: transmit theinformation simultaneously with another user terminal in a synchronizedmanner, or at a predefined time offset compared to another user terminalwhen more than one user terminal transmits the information. 22.(canceled)
 23. The apparatus of claim 15, further comprising aninterface configured to: receive the information; and the processor isapplicable to a base station and further configured to: monitor datavolume of ongoing end-to-end communication between at least two userterminals on the basis of the received information; and control thequality of service of end-to-end communication between the at least twouser terminals on the basis of the received information.
 24. Theapparatus of claim 15, wherein the processor is applicable to a basestation and is further configured to: redistribute radio resources ofthe mobile communication on the basis of the received information. 25.The apparatus of claim 15, wherein the processor is applicable to a basestation and is further configured to: decide on the basis of thereceived information whether to apply conventional radio communicationvia the base station or the direct communication between the at leasttwo terminals or not.
 26. The apparatus of claim 15, wherein theprocessor is applicable to a base station and further configured to:control the quality of service of the communication between the at leasttwo terminals by more than one base station; and communicate with atleast one other base station in order to coordinate the quality ofservice of the end-to-end communication between the at least twoterminals.
 27. The apparatus of claim 15, wherein the processor isapplicable to a base station and further configured to: manage a virtualradio bearer database corresponding to the radio bearers applied in thedirect communication between the at least two user terminals; and updatethe virtual radio bearer database on the basis of the receivedinformation.
 28. The apparatus of claim 15, wherein the processor isapplicable to a base station and further configured to: controlre-transmissions of the direct communication link between the at leasttwo user terminals such that the re-transmissions are performed throughthe conventional radio communication link via the base station. 29.(canceled)
 30. A computer program product embodied on a distributionmedium readable by a computer and comprising program instructions which,when loaded into an apparatus, execute a method, comprising: applyinguplink signaling in mobile communication, wherein the signalingcomprises information determined by a device as related to the trafficstatus of a direct communication link between at least two userterminals being the terminating points of the communication; andtransmitting the information in the uplink to a base station from atleast one user terminal involved in the direct communication linkthereby enabling the base station to control the quality of service ofan end-to-end communication between the at least two user terminalsbased on the received information.